Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications. In a UMTS network, a wireless user equipment (UE) may have the capability of transmitting a minimum set of transport format combinations (TFCs) or a minimum set of enhanced transport format combinations (E-TFCs) in the uplink transmission. These minimum sets are described in detail in 3GPP Technical Specification (TS) 25.331. The UE may be configured to transmit both minimum sets (TFCs and E-TFCs) in a multiple radio access bearers (Multi-RAB) mode. According to 3GPP TS 25.214, when the total transmit power of the UE exceeds a maximum allowed value, which may be determined by the network, the UE applies power scaling so that the total transmit power is equal to or less than the maximum allowed power, in order to support the minimum sets of TFC/E-TFC data in addition to the transmission on the uplink high speed dedicated physical control channel (HS-DPCCH).
Due to the power scaling, there is a possibility that the data of the HS-DPCCH is not decoded reliably on the network side (receiving end). For example, if the hybrid automatic repeat request (HARQ) acknowledgement (ACK) is decoded as a discontinuous transmission (DTX), the network might end up retransmitting the data, which will be decoded as duplicate data and discarded by the UE. This will result in sub-optimal usage of the radio resources, and degraded effective data throughput at the UE, which is already operating in peak power range. In another scenario, if the HARQ negative ACK (NAK) is decoded as an ACK, the network might end up transmitting new data, which will result in discarding the previous HARQ transmission time interval (TTI) data at the UE.